The present invention relates generally to clamping devices for holding flexible sheet material and the like and deals more specifically with a releasable clamping device for holding flexible bulletin face sheet material of the type upon which a large scale graphic is printed and generally supported by a billboard structure and the like.
There has been a substantial increase recently in the use of flexible sheet material as a bulletin face for recording large scale graphics of the type that are displayed on roadside billboards and in large open areas such as for example, transporation terminals, shopping centers and the like. Flexible bulletin face sheet material is generally light weight compared to one system of displaying large scale graphics wherein a number of plywood sections are used with each face displaying a portion of the complete graphic. The sections are usually hoisted into place by a crane and bolted or secured to a framework or structure of some type similar to a roadside billboard and the collective faces of the assembled sections display the complete graphic. The plywood sections and associated graphic portion printed on each of the faces are expensive to produce, difficult to erect and the process is highly labor intensive. In contrast to the plywood section display system, a system using flexible bulletin face sheet material often can be positioned and mounted on a billboard structure without the need of heavy hoisting equipment and the ability to do so is one major reason the flexible sheet display system is preferable to the plywood system.
One flexible bulletin face mounting system uses a flexible bulletin face sheet material that is fabricated with a hem or cuff at the sides or edges around its perimeter. An elongated metal bar is inserted into the cuff by an installer positioned at or near the top of the billboard structure. The hem is scalloped at regularly spaced intervals to expose and provide access to an elongated metal bar that is inserted into the cuff and to which a holding device of some type such as a hook is attached. The hook in turn is generally coupled to a tightening device located on the backside of the billboard structure. The tightening device is operated to pull on the bar and accordingly the bulletin face material. The tension produced across the bulletin face by the tightening device reduces or removes wrinkles in the bulletin face and holds the bulletin face in position against the billboard structure.
One problem usually associated with the mounting and holding of the above-described flexible bulletin face is that the installer must carry and insert a relatively long bar, approximately 14 feet in length through the cuff along the edge of the material. The handling and placement of the bar is sometimes difficult and cumbersome and exposes the installer to the possibility of losing his balance, falling to the ground or some other part of the billboard structure and possibly suffering a serious injury.
Another problem associated with the aforementioned flexible bulletin face and its method of mounting to a billboard is that the scallops in the flexible bulletin face often appear at fixed spaced intervals along the cuff and sometimes are not in alignment with the placement of the holding device on the billboard structure. Consequently, alignment and registry of the graphic printed on the bulletin face with another portion of the graphic contained on a billboard extension may be difficult and in some cases alignment may not be possible and the display may not be pleasing to a viewer.
Yet another problem associated with the aforementioned flexible bulletin face is a higher labor cost incurred during manufacturing due to the inclusion of a cuff along the material's edge for receiving the metal folding bar.
A further problem associated with the above-mentioned cuff type bulletin face and associated holding device is that it is difficult and often inconvenient to reposition the bulletin face on the billboard surface.
Yet a further problem associated with the cuff type bulletin face and associated mounting system is that the face, when rolled for carrying or storage has a "bar bell" appearance and consequently, a number of such rolled bulletin faces cannot be easily stacked or stored.
It would be desirable therefore to provide a clamping device for holding flexible sheet material and the like, specifically the type used for providing a bulletin face upon which large scale graphics are printed, that overcomes the above-mentioned problems.
It is an object therefore of the present invention to provide a clamping device for holding flexible sheet material that overcomes the above described problems.
It is another object of the present invention to provide a clamping device of the type for use with a billboard structure to hold a cuffless, flexible bulletin face sheet material upon which a desired graphic is printed and displayed.
It is yet a further object of the present invention to provide a clamping device that is positionable and operable at any desired position across the face of a flexible sheet material.
It is yet another object of the present invention to provide a clamping device that is easily operable between a clamping condition and a non-clamping condition to facilitate the positioning of a flexible bulletin face on a billboard structure and for clamping the bulletin face to the structure.